JP2010286343A - Radar receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that a method for analogously synthesizing and generating a signal in a circuit enables the signal to be expanded in a dynamic range only by dividing the reception signal of a radar receiver into small and large signals, but causes deformed linearity to occur in the input/output characteristic of the receiver. <P>SOLUTION: The weather radar receiver includes: a radar reception receiver wherein a radar reception signal is divided into an IF signal of small signal and an IF signal of large signal by a directional coupler 201; a digital demodulator that digitizes and demodulates the IF signal of small signal and the IF signal of large signal and synthesizes them later; and a signal processor for processing the signal demodulated by the digital demodulator. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a weather radar receiver that requires a wide dynamic range in order to target small objects such as raindrops.

The radar device transmits an electromagnetic wave at a certain time, and the radar receiver required the electromagnetic wave to travel back and forth between the radar device and the target based on the time when the reflected wave from the target is received. Time is calculated and the distance to the target is calculated based on the time.

 As shown in FIG. 1, a general radar receiver amplifies a radar wave transmitted from a radar transmitter, reflected by a target and received by an antenna 101 by a low noise amplifier 103, and from a local oscillator 107 by a mixer 105. A beat frequency component is extracted by mixing with the local oscillation signal to be output, and the differential frequency is extracted as an intermediate frequency component (IF signal) by the low-pass filter 109.

  For example, in a weather radar receiver, a target object is a mist like raindrops, and the reception level is very small. In general, in a radar receiver that handles a target with a low reception level, the reception sensitivity is improved by making the low-noise amplifier 103 multi-stage. However, if the multi-stage amplifier is used, the saturation level is lowered, so that the dynamic range is degraded. Has the disadvantage of becoming intense.

Further, the radar wave received by the antenna 101 is branched into a large signal route and a small signal route, and the IF signal of the large signal route and the IF signal of the small signal route are synthesized in an analog manner to generate a signal. Have been proposed (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 2000-137071 JP 2008-215952 A

  However, as described above, the method of generating a signal by dividing the received signal of the radar receiver into a small signal and a large signal and synthesizing them in a circuit in an analog manner can expand the dynamic range, but The linearity in the input / output characteristics is distorted.

In other words, in the method of generating a signal by synthesizing in an analog manner, the input / output characteristics of the radar receiver are not linear because the impedance of the elements of the electronic circuit of the synthesizer fluctuates between a small signal component and a large signal component. is there. In a radar receiver, the expansion of the dynamic range and the maintenance of the linearity of the input / output characteristics are both necessary elements, and both must be established.

In order to solve the above problems, the present invention provides:
In weather radar receivers,
A radar receiver that separates and outputs a radar received signal into a small IF signal and a large IF signal by a directional coupler;
A digital demodulator for digitizing and synthesizing the small signal IF signal and the large signal IF signal;
A signal processing unit that processes a demodulated signal by the digital demodulation unit;
The meteorological radar receiver.

In the present invention, since the radar receiver having different output terminals depending on the signal level is used, the dynamic range can be expanded while maintaining linearity.

According to the present invention, by using a large signal IF and a small signal IF, in a weather radar receiver using a reflected wave from an extremely small object such as raindrops, the dynamic range can be expanded and the sensitivity can be increased. it can. Further, by synthesizing the large signal IF and the small signal IF in the state of a digital signal, input / output linearity necessary for accurately grasping the strength, distance, and the like can be realized.

General radar receiver Schematic diagram of a radar receiver according to the present invention Overall view of the system according to the present invention Dynamic range expansion

A preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a general radar receiver. The radar device reflects the radar wave transmitted from the radar transmitter to the measurement target, receives the reflected wave with the antenna of the radar receiver, and processes the signal to obtain information such as the position of the measurement target. .

In the general radar receiver shown in FIG. 1, the radar reflected wave received by the antenna unit 101 is amplified by the amplifier 103 and mixed with the local oscillation signal output from the local oscillator 107 by the mixer 105, thereby generating a beat frequency component. Extracted and extracted as an intermediate frequency signal (IF) by the low-pass filter 109.

When the IF output signal port has one system as described above, the dynamic range and linearity (linearity) of the signal output from the output signal port depend on the characteristics of the amplifier in the circuit, and generally the dynamic range. It has been said that the performance limit is 80 dB and the linearity is about 70 dB.

On the other hand, according to the method shown in FIG. 2, the IF output signal port can have two systems of high power and low power.

That is, the radar reflected wave received by the antenna 101 is made into one input and two outputs by the directional coupler 201, and one of the outputs is amplified by the low noise amplifier 203. Thereafter, the beat frequency component is extracted by mixing with the local oscillation signal output from the local oscillator 211 by the mixers 205 and 209 and extracted as the intermediate frequency signals (IF1, IF2) by the low-pass filters 213 and 215, as in the conventional example.

Here, since IF1 is transmitted through an amplifier with low noise and high amplification factor, the component of signal power above a certain level is saturated, and IF1 taken out as a fluctuating signal was originally received by antenna 101. It is a small signal component in the signal. One IF2 is the other large signal component.

FIG. 3 is a system schematic diagram of a receiving apparatus using the radar receiver of FIG. That is, a small signal IF signal and a large signal IF signal are taken out from the radar receiver 301, each IF signal is demodulated by the digital demodulator 303, converted into a digital signal by the AD converter in the same 303, the The signals are combined in the converted digital signal state and transmitted to the subsequent signal processing unit 305.

FIG. 4 is an example showing that the dynamic range is expanded by taking out two systems of IF signals. In other words, for example, if there is a small signal with a dynamic range of 52 dB and a large signal with a dynamic range of 60 dB, and the overlapping area is 8 dB, the dynamic range that combines the small signal and the large signal is added and overlapped. The subtracted area is 104 dB.

In the present invention, in a state where the dynamic range is expanded as described above, the signal digitized by the AD converter in the digital demodulator 303 is synthesized to prevent the signal from being non-linear by the analog element, Maintaining linearity as the range is expanded.

In the present invention, FIG. 2 is a schematic diagram. For example, an attenuator is inserted between the distributor 207 and the mixer 205 to attenuate the local oscillation signal.

Further, regarding the small signal and the large signal, the respective ranges are arbitrary, and the threshold value is not uniquely determined.

101 ... antenna, 103 ... amplifier,
105 ... mixer, 107 ... local oscillator,
109 ... LPF,
201 ... directional coupler, 203 ... low noise amplifier,
205 ... mixer, 207 ... distributor,
209 ... mixer, 211 ... local oscillator,
213 ... LPF, 215 ... LPF,
301: Radar receiver 303: Digital demodulator,
305... Signal processing unit.

Claims (1)

In weather radar receivers,
A radar receiver that separates and outputs a radar received signal into a small IF signal and a large IF signal by a directional coupler;
A digital demodulator for digitizing and synthesizing the small signal IF signal and the large signal IF signal;
A signal processing unit that processes a demodulated signal by the digital demodulation unit;
A meteorological radar receiver.